1Field of the Invention
The present invention relates generally to medical fluid infusion systems for delivering a selected medical fluid to a patient, and more particularly to an improved apparatus and method for quickly and easily clearing small quantities of detected air or gas from the detection field of an air-in-line sensor in a patient fluid infusion system.
Medical fluid infusion systems are generally known in the art for use in delivering one or more selected fluids through appropriate tubing and/or a catheter or the like to a patient. Such infusion systems often utilize a relatively compact electronically controlled pump adapted for mounting onto a conventional portable medical equipment pole and including an appropriate pump element or elements for closely regulating fluid delivery to the patient. One example of an infusion pump of this general type is marketed by MiniMed Technologies of Sylmar, Calif. under the name MiniMed III.
Modern infusion pumps used in patient fluid infusion systems are commonly equipped with an air-in-line sensor for monitoring fluid delivery through a length of tubing and to activate an alarm and/or disable the pump upon detection of air. In this regard, ultrasonic detectors are known in the art and have the capability to determine the Volume of air in a tubing line and to activate the alarm or halt pump operation when the detected air volume exceeds a predetermined and potentially harmful threshold. Such air detectors may operate in conjunction with the pump to decrement an accumulated fluid infusion record in accordance with the volume of air bubbles detected in the infusion tubing line.
Relatively small air or gas bubbles may commonly occur at the discharge side of the pump element, apparently as a result of outgassing at that location. Accordingly, the detection field of the air-in-line sensor is typically located at the discharge side of the pump element to insure detection of air within the infusion line. In most instances, the volume of air or gas present at the discharge side of the pump is sufficiently small such that no significant patient hazard results and there is no need to interrupt pump operation. Instead, the threshold setting for the air-in-line sensor is simply adjusted to allow continued pump operation when small air volumes are detected.
In some instances, however, small air bubbles can temporarily stick along the tubing line without obstructing continued fluid flow to the patient. When this occurs within the detection field of the air-in-line sensor, the sensor will detect the small bubble or bubbles as an elongated and thus significantly greater air volume, whereby the sensor will respond to activate the alarm or to halt pump operation. In this event, it is necessary for nursing personnel or the like to conduct a visual check of the infusion system and, if the actual volume of detected air or gas is medically is insignificant, manipulate the infusion tubing and/or the pump element to clear the air from the detection field of the sensor so that the pump can be restarted. Such manipulation of the infusion tubing typically involves manual tapping or shaking of the infusion tubing line and/or pump components connected thereto to dislodge and move stuck air bubbles to a location downstream of the air-in-line sensor. False alarms of this type can occur on several occasions throughout the course of a nursing shift, and are viewed by nursing personnel as a significant nuisance.
The present invention provides a significant improvement in medical fluid infusion systems by adapting the infusion pump for rapid clearing of small quantities of air or gas from the detection field of an air-in-line sensor, without requiring significant manual handling of system components.